Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $112.86   11.251%   $125.5579   $125.56   $125.55   $125.60  
  Purchase #2 $22.87   8.285%   $24.7648   $24.76   $24.75   $24.80  
  Purchase #3 $69.54   8.414%   $75.3911   $75.39   $75.40   $75.40  
  Purchase #4 $241.62   10.173%   $266.2   $266.20   $266.20   $266.20  
  Purchase #5 $148.50   4.755%   $155.5612   $155.56   $155.55   $155.60  
  Purchase #6 $29.74   3.390%   $30.7482   $30.75   $30.75   $30.70  
  Purchase #7 $195.53   10.752%   $216.5534   $216.55   $216.55   $216.60  
  7 purchase totals = $820.66       $894.7766   $894.77   $894.75   $894.90